Devices and methods for measuring the volume of a cavity are known. Many of said devices and methods use the Helmholtz resonator principle for determining the volume of gas inside the cavity. This principle, which has an apparently simple basis of application, is based on coupling a resonator, generally a tube, in fluid communication with the cavity the volume of which is to be known. The tube and cavity are filled with a gas, usually air, and the volume of gas located inside the tube is oscillated by means of a blower. The system formed by the gas of the tube and the gas of the cavity is represented as a system having one degree of freedom, in which the gas of the tube behaves like a mass oscillating on the gas of the cavity, the cavity behaving like a spring.
Devices applying the Helmholtz principle comprise means that allow determining the resonance frequency of the cavity. Considering that the process carried out is adiabatic, the volume V of the cavity is obtained according to formula:V=A*c2/4*π2*f*l wherein,    A is the area of the cross section of the tube,    c is the speed of sound in the medium where the measurement is taken,    f is the resonance frequency of the cavity the volume of which is to be measured, and    l is the length of the tube.
Patent application JP7083730 A describes a device for measuring the inner volume of a cavity applying the Helmholtz resonator principle and comprising a hollow body coupleable to said cavity, such that the inner volume of the cavity and the inner volume of the hollow body are communicated.